Food allergy and intolerance

If you, or someone in your care, has a severe allergic reaction, call your local emergency number (for example 911 in the US and Canada, 112 across the EU and many countries, 999 in the UK, or 000 in Australia) for an ambulance. The person having the reaction should not stand or walk. Administer an adrenaline (epinephrine) injector (such as EpiPen® or Anapen®) into the outer mid-thigh. Further doses of adrenaline may be given if there is no response after 5 minutes. Give adrenaline first, then an asthma reliever puffer, if required.

Allergy and intolerance are different#

Food allergy and food intolerance are commonly confused, because the symptoms of food intolerance sometimes resemble those of food allergy. However, they are not the same.

A food allergy is an immune response: the immune system reacts to a usually harmless food protein as if it were toxic. These proteins are called allergens. Allergens may come from foods, pollens, house dust, animal dander (including fur, wool and pollens brought into the home by pets) and molds.

Food intolerance is a chemical reaction that some people have after eating or drinking certain foods. It is not an immune response. It does not cause severe allergic reactions (anaphylaxis), and it does not show up on allergy testing. Food intolerance has been associated with conditions such as asthma, irritable bowel syndrome (IBS) and chronic fatigue syndrome.

Food allergy is increasing#

Allergies are on the increase worldwide, and food allergies have also become more common. Most allergies appear during the first year of life. Cow’s milk allergy is one of the most common allergies in early childhood, and most children grow out of it before they start school. More research is needed into the causes, diagnosis and treatment of food allergy.

Allergy can be inherited#

Children who have one family member with allergic disease (including asthma or eczema) have a higher risk of developing allergy. Most children with food allergy do not have parents with food allergy. However, if a family already has one child with food allergy, their brothers and sisters are at a slightly higher risk of having food allergy themselves, although that risk is still relatively low.

Symptoms of food allergy and intolerance#

It can be difficult to tell the symptoms apart. Symptoms of food allergy usually develop very soon after eating the food. Symptoms of food intolerance can be immediate, but they may also take 12 to 24 hours to develop. Intolerance reactions are usually related to the amount of food consumed and may not occur until a certain threshold amount is eaten – an amount that varies from person to person.

The symptoms of food allergy and intolerance can also be caused by other conditions, so it is important to see your doctor for a proper diagnosis.

Symptoms of food intolerance can include#

• Nervousness, tremor, sweating, palpitations or rapid breathing
• Headache or migraine
• Diarrhea
• Burning sensations on the skin
• Tightness across the face and chest
• Asthma-like breathing problems
• Rashes such as hives, or the stomach upset of irritable bowel syndrome

Symptoms of mild to moderate food allergy can include#

• Swelling of the lips, face and eyes
• Hives or welts
• Tingling mouth
• Abdominal pain or vomiting
• Skin rashes, such as hives (urticaria) or atopic dermatitis

Severe allergic reactions (anaphylaxis)#

Anaphylaxis is a severe allergic reaction that needs urgent medical attention. Within minutes of exposure to the allergen, a person can have potentially life-threatening symptoms, which may include:

• Difficult or noisy breathing
• Swelling of the tongue
• Swelling or tightness in the throat
• Wheeze or persistent cough
• Difficulty talking or a hoarse voice
• Persistent dizziness or collapse
• Becoming pale and floppy (in young children)

Several factors can influence the severity of anaphylaxis, including exercise, heat, alcohol, the amount of food eaten, and how the food is prepared and consumed.

To prevent severe injury or death, a person with anaphylaxis needs an injection of adrenaline. They should not be allowed to stand or walk. Further doses may be given if there is no response after 5 minutes. Give adrenaline first, then an asthma reliever puffer, if required.

People considered by their doctor to be at risk of anaphylaxis are prescribed an adrenaline injector (such as an EpiPen® or Anapen®), which contains a single fixed dose of adrenaline. They should also have an action plan for anaphylaxis. Adrenaline injectors are designed to be used by non-medical people and are available directly from a pharmacy.

Causes of food allergy#

Peanuts, tree nuts, eggs, cow’s milk, wheat, sesame, fish, shellfish and soy cause the majority of food allergic reactions, and these foods are also the most common causes of anaphylaxis. Peanut allergy is one of the most common allergies in older children, as only about one in four children will outgrow it.

Causes of food intolerance#

Foods that tend to cause intolerance reactions in sensitive people include:

• Dairy products, including milk, cheese and yoghurt
• Chocolate
• Eggs, particularly egg white
• Flavor enhancers such as MSG (monosodium glutamate 621)
• Food additives
• Strawberries, citrus fruits and tomatoes
• Wine, particularly red wine
• Foods containing amines or salicylates

Finding the allergen#

When symptoms appear within a few minutes of eating a particular food, pinpointing the cause is straightforward. If the cause is unknown, diagnostic steps may include:

• Keeping a food and symptoms diary to check for patterns
• Removing all suspect foods for 2 weeks, then reintroducing them one at a time to test for reactions (except in cases of anaphylaxis)
• Skin prick tests using food extracts

This should be done under the supervision of a clinical immunology/allergy specialist or dietitian. Only evidence-based allergy tests are recommended.

Treating food allergy or intolerance#

The simplest way to treat a food allergy or intolerance is to eliminate the offending food or foods from the diet. Sometimes the body can tolerate the food if it is avoided for a time, then reintroduced in small doses – this is more common with food intolerances. Before you eliminate or reintroduce foods, seek advice from a clinical immunology/allergy specialist or dietitian.

Preventing food allergy in children#

Allergy prevention in children is an active area of research. Findings to date indicate that:

• Prenatal – there is no conclusive evidence that avoiding allergens during pregnancy helps prevent allergies.
• Postnatal – exclusive breastfeeding during the first 4 to 6 months appears to protect against the development of allergies in early childhood.
• Introducing solid foods (including those considered to be allergenic) around 6 months, but not before 4 months, is recommended, preferably while continuing to breastfeed. Avoidance of a food by a woman while breastfeeding is not recommended.
• Soymilk formula has not been shown to prevent the development of allergies in children.
• Partially hydrolysed cow’s milk-based formula (commonly referred to as HA formula) is not recommended to prevent the development of food allergy.

Severe food allergy in schools and childcare#

Allergic reactions, including anaphylaxis, are common, although deaths from anaphylaxis are rare. Banning particular foods in schools and early childcare is not recommended, as it can create a sense of complacency and is difficult to monitor and enforce. A better approach is to educate staff, students and the wider community about the risks of anaphylaxis and to put strategies in place to minimize exposure to known allergens.

Food labels and allergen avoidance#

You should only avoid foods to which you have a diagnosed allergy. It helps to learn the terms used to describe these foods on labels, for example:

• Milk protein – milk, non-fat milk solids, cheese, yoghurt, caseinates, whey, lactose
• Lactose – milk, lactose
• Egg – eggs, egg albumen, egg yolk, egg lecithin
• Gluten – wheat, barley, rye, triticale, wheat bran, malt, oats, cornflour, oat bran
• Soy – soybeans, hydrolysed vegetable protein, soy protein isolate, soy lecithin
• Salicylates – for example, strawberries and tomatoes

Food labelling laws require certain foods and substances to be declared when they are present, including when they are an ingredient, part of a compound ingredient, a food additive or part of a food additive, or a processing aid. These commonly include:

• Cereals that contain gluten, and their products
• Shellfish and their products
• Eggs and egg products
• Fish and fish products
• Milk and milk products
• Tree nuts
• Sesame seeds and their products
• Peanuts
• Soybeans and their products
• Added sulphites in concentrations of 10 mg/kg or more
• Royal jelly, bee pollen and propolis (presented as food or present in food)

Key points#

• A food allergy is an immune response to a usually harmless food protein, while food intolerance is a chemical reaction and does not cause anaphylaxis.
• Allergies are increasing worldwide, and food allergy is among the most common in early childhood.
• Anaphylaxis is a medical emergency: give adrenaline first and call for an ambulance.
• People at risk of anaphylaxis should carry an adrenaline injector and have an action plan.
• See your doctor for a proper diagnosis before eliminating foods from your diet.

Where to get help#